1. Field of the Invention
The present invention relates to a indexing and locking mechanism for use in a drive train for a motor vehicle to provide for the smooth shifting between gear positions and provide for the braking of intermediate drive shaft in a neutral position. The present invention also relates to a drive train having a free wheel clutch operating in parallel with a centrifugal clutch. The indexing and locking mechanism and the drive train are useable on an all terrain vehicle (“ATV”), scooters or any other recreational vehicle.
2. Description of Related Art
Various manual transmissions for internal combustion engine driven vehicles (e.g., an ATV or a scooter) are known in the art. In a typical arrangement, an internal combustion engine provides energy to drive a drive shaft through suitable engine gearing. This can be accomplished by a belt-driven constant velocity transmission (CVT) that acts, preferably through a manual transmission, on a driven shaft that is connected to at least one driving wheel. A forward gear, a reverse gear, or neutral positions can be selected as desired by the manual transmission.
In the prior art, the drive unit transmits power to the drive shaft through a centrifugal clutch and an interposed CVT. The centrifugal clutch transfers engine torque to the drive shaft a certain engine speeds (e.g., 4000 rpm) and forms a rigid drive connection between the drive unit and the driven shaft above a certain engine speed. At lower engine speeds, no engine torque is transmitted between the drive unit and the driven shaft. This has potential adverse impacts when the engine is used, for example, in an ATV and operated at low engine speeds. When in an idling state, no engine torque and hence no braking moment is transmitted to the driven shaft. When the ATV is positioned on a hill, the ATV picks up speed. The engine cannot control the speed. At low speeds, the engine torque can serve as a braking moment for the driven shaft.
The freewheel clutch can be locked up so as to transmit torque in one direction and to freewheel in the other direction. The purpose of the freewheel clutch is to permit an engine braking effect to act on the driving wheel at low engine speeds, when the centrifugal clutch is not activated. In this way, at low engine speeds, torque can be transferred to the driven shaft. At high engine speeds no engine torque is transferred to the drive shaft through the freewheel clutch. Freewheel clutches, and in particular sleeve-type freewheel clutches, often produce a negative secondary effect, namely, that as a result of friction, a small amount of torque will be transferred in the free-wheel direction. In particular, in the case of rotational conformity of the drive unit, as in the case of four-cycle engines, a small amount of torque will be transferred from the drive unit through the freewheel clutch to the drive shaft. If a gear position is selected from the neutral position by the manual transmission, a jolt or a loud noise is produced. As such, it is desirable to provide a brake to eliminate any rotation associated with the small amounts of torque. Others have tried to provide such a brake.
DE 44 22 427 A1 describes a reverse gear selector for a motor vehicle change-speed gearbox that incorporates a braking device that is actuated during the gear-change process by part of the selector mechanism, and which is used to brake a gear shaft that is still spinning as the result of residual momentum. In this, a part of the gear-change device actuates a switch that allows an auxiliary force to act for a specific period of time on a servo that activates a braking device that in turn acts on the gear shaft that is still spinning. The servo device is in the form of a solenoid that acts through a selector fork, a selector rod, or directly on the synchromesh ring of a forward gear.
DE 100 09 584 A1 shows a multi-speed manual transmission for motor vehicle; this comprises a separating clutch, a drive shaft, and a driven shaft, on which there are gear wheels that mesh with each other in order to provide various gear ratios. The gear wheels for the various gear ratios can be locked positively to the gear shaft through a clutch. Thus, the gear ratios are synchronized centrally, because the gear shaft is slowed down by a flywheel brake when a higher gear is selected, whereas the gear shaft is accelerated by an central engine control unit when changing down to a lower gear. Central synchronization makes it possible to dispense with a synchronizing unit for each gear ratio that is selected.
DE 198 42 478 A1 describes an hydraulic clutch brake for gearboxes. Retardation of the gear shafts, which is usually taken care of by the clutch stop, is effected in that the load on the gear shafts is increased. This can be done, for example, by increasing the hydraulic load of a pump that is driven by a gear shaft.
These braking devices for manual transmissions, however, have rather complex constructions and have relatively high design and production costs.